ScrollMagic - The jQuery plugin for magical scroll interactions.
GitSpo - Measure & engage your open-source community
WOW.js - Animate elements on-scroll to catch attention. Such Magic.
Devo - Devo delivers real-time operational & business value from analytics on streaming and historical data to operations.
Lax.js - Create beautiful & smooth animations when you scroll
LibHunt - LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.